1. Field of the Invention
The present invention relates to a process for the production of benzene derivatives of chemical formula (I), which are useful as intermediates for agricultural chemicals, fine chemicals or pharmaceuticals such as anti-inflammatory analgesics. ##STR2##
In chemical formula (I), X is a halogen, R.sub.1 and R.sub.2 are the same or different, R.sub.1 is a hydrogen atom or lower alkyl radical of carbon number 1-6, R.sub.2 is a hydrogen atom or COOR.sub.3, and R.sub.3 is a hydrogen atom or lower alkyl radical of carbon number 1-6.
2. Discussion of the Background
Benzene derivatives of the above chemical formula (I) are especially useful starting materials for the production of valuable 2-{4-(2-oxocyclopentylmethyl)phenyl} propionic acid, which is useful as an anti-inflammatory agent.
Several methods have been reported to produce benzene derivatives in aforesaid chemical formula (I).
According to Japan Public Patent No. 87-129250 and No. 87-155237, the reaction of 2-(para-methylphenyl)propionic acid and a halogenating agent under a radical generating agent has been disclosed.
In Japan Public Patent No. 81-13840, a method of producing 2-(4-halomethylphenyl) propionic acid by reaction of 2-phenylpropionic acid and methylal under a strong Lewis acid such as aluminum chloride (AlCl.sub.3) and tin chloride (SnCl.sub.4) has been disclosed.
In the aforesaid conventional methods, the purity of the final product is reduced due to the formation of by-products during the radical reaction. Consequently, a complicated refining process is required to improve the purity of the final product. In addition, in order to produce the starting material, 2-(para-methylphenyl)propionic acid, several reaction steps are required. Thus, the conventional processes are both complicated and expensive.
Therefore, it is desirable to provide a method of producing benzene derivatives of chemical formula (I) having improved purity from commercially available starting materials.